1. Field of the Invention
The present invention relates to a reclosable fastener with slider for use in reclosable packages. Particularly, the present invention is directed to such fasteners for use in high-pressure environments, such as in high-pressure pasteurization processes.
2. Description of Related Art
Plastic bags are in widespread use in a varied and diverse number of household and commercial applications. An advantage of plastic bags is the ease of opening and resealing of such containers. FIG. 13 shows a reclosable plastic bag 1300, which includes first and second opposing body panels 1340 connected to each other along a pair of sides 1345, 1347 and a bottom, in which the bottom extends between the pair of sides. The plastic bag 1300 includes a fastener, such as engageable tracks or a zipper 1330, extending along a mouth formed opposite the bottom of the plastic bag. The zipper 1330 generally includes a male track 1330a and a female track 1330b. The male track includes a male profile having a first depending fin or flange 1331a extending downward from the male profile. Likewise, the female track 1330b includes a female profile having a second depending fin or flange 1331b extending downward from the female profile. The first and second fins can be extruded separately from the body panels 1340 and then thermally fused to the respective first and second body panels 1340.
In some embodiments, known as press-to-close fasteners, the male and female tracks 1330a, 1330b are rolled or pressed into interlocking engagement so as to securely close the bag 1300. Alternatively, and as depicted in FIG. 13, a plastic slider 1310 can be provided to ride along the tracks 1330a, 1330b of the zipper 1330. If the slider 1310 is pulled in one direction, the bag 1300 is sealed closed; if the slider 1310 is pulled in the opposite direction, the bag 1300 is opened. For strength and longevity, a track end termination 1337 is usually desired. The termination 1337, among other things, strengthens the end of the zipper 1330, and prevents the slider 1310 from sliding off of the zipper 1330. Such termination 1337 can be in the form of a clip, as illustrated, or can be an integrally formed region of the tracks that is strong enough to meet the required design criteria. Such region can be made by fusing predetermined regions at the end of the zipper 1330, such as by heat or ultrasonic welding techniques.
Specific details regarding the operation of a conventional slider-operated resealable bag are set forth, for example, in U.S. Pat. No. 6,611,996, the entire disclosure of which is incorporated herein by reference.
Such conventional packages generally have been considered satisfactory for their intended purpose. However, when undergoing processing involving extreme environments, such as high pressurization, or those involving pressurization and heating, the presence of the slider can result in failure in some bag constructions.
Furthermore, certain zippered resealable bags include a header portion extending beyond the resealable track and slider. For example, the header can be sealed at its upper end by a packager or processor to form a resealable bag with a tamper-evident seal. This is desirable for consumer use to assure a secure seal, while the slider provides easy and reliable reclosable function.
FIG. 14 illustrates an example of a reclosable bag 1400 having a slider 1427 and first and second header portions 1418 and 1482 divided by a line of weakness 1484, such as a perforation or thinned material region. The figure illustrates a bag 1400 that has been filled with a product 1480 and sealed along a top edge 1483. The user can tear the sealed upper header 1482 along the line of weakness 1484, with the lower header portion 1418 remaining in tact. Seals 1472 along the sides and bottom, which define the extent of a storage region of the bag, are unaltered.
After opening or removal of the header 1482, the user may reseal the bag 1400 using the provided slider 1427, which travels along the track 1416 of the reclosable fastener 1428.
When processing a bag of this type under pressure, failure can occur due to the conventional slider preventing surrounding film from laying flat, thereby causing pockets of air between opposite panels of the header and air within the slider body 1427. Under pressure, the air within these pockets compresses and causes localized film stretching and failure of the film.
For the foregoing reasons, it is apparent that there remains a need for an efficient and economic system and method for preparing a zippered bag capable of withstanding pressurized treatment, particularly treatment at very high pressures.